When the EEPROM data is read from flash, it can contain pre-calibration
data, which can save calibration time.

Note that group_cal can save 30% bootup calibration time, and dpd_cal can
save 75% channel switching time.
Tested-by: NBo Jiao <bo.jiao@mediatek.com>
Signed-off-by: NRyder Lee <ryder.lee@mediatek.com>
Signed-off-by: NFelix Fietkau <nbd@nbd.name>